Hydraulic master cylinder assembly



2 Sheets-Sheet 1 Aug. 27, 1957 c. w. .loHNsoN ETAL HYDRAULIC MASTER CYLINDER ASSEMBLY Filed May 3, 1955' i Q Il h@ Aug. 27, 1957 c. w. JOHNSON y15T AL 2,803,947

HYDRAULIC MASTER CYLINDER ASSEMBLY Filed May 3. 1955 2 Sheets-Sheet 2 F'/ G. 9 CIL/572e w. Joh/msm INVENTUR.

United States Patent U HYDRAULIC MASTER CYLINDER ASSEMBLY Chester W. Johnson and Herbert H. Shanklin, Butte, Mont.

Application May 3, 1955, Serial No. 505,606

3 Claims. (Cl. 60 54.6)

The present invention relates to a hydraulic master cylinder as used in a brake system and in particular to one having a compound high and low pressure piston.

The primary object of the present invention is to provide a hydraulic master cylinder assembly which applies high pressure to the brakes in a brake system without the need for hard pedal pressure.

Another object of the present invention is to provide a hydraulic master cylinder assembly having a low pressure piston and providing means for holding the low pressure piston against backing up movement in the pressure chamber when a high pressure piston increases the pressure therein.

A further object of the present invention is to provide a hydraulic master cylinder assembly of sturdy construction, simple in design and structure, one easily assembled and disassembled, and one which is economical to manu facture and distribute.

These and other objects and advantages of the present invention will be fully apparent from the following description when taken in connection with the annexed drawings, in which:

Figure l is a side elevational view in cross-section of the master cylinder assembly of the present invention,

Figure 2 is an end view, greatly reduced, taken on line 2 2 of Figure l,

Figure 3 is an end View in cross-section, greatly reduced, taken on line 3 3 of Figure 1,

Figure 4 is an end View in cross-section on line 4 4 of Figure 1,

Figure 5 is a detailed view in cross-section on line 5 5 of Figure l,

Figure 6 is a vertical view as seen on line 6 6 of Figure 5,

Figure 7 is a partial view in cross-section of the assembly shown in Figure l after pressure of the brake pedal has initiated movement of the piston and the actuating member of the present invention, and

Figure 8 is a side view in elevation somewhat reduced, showing in dotted lines the movement of the actuating member with the attached portion of the brake pedal connection.

Referring in greater detail to the drawings in which like numerals indicate like parts throughout the several views, the present invention consists in a hydraulic master cylinder assembly comprising a cylinder 10 having one end closed by a cap 11 and the other end closed by a cap 12, the latter cap having an outlet 13 adapted to be connected to a hydraulic brake system.

A hollow actuating member 14 having both of its ends closed is mounted within the cylinder 10 for reciprocal movement toward and away from the outlet 13 and has one end portion 15 exterior-ly of the other end of the cylinder opposite to the outlet 13.

An annular piston 16 is slidably mounted upon the other end portion 17 of the actuating member 14 and subdivides the space Within the cylinder 10 into a iluid equalizing chamber indicated in Figure 1 by the reference ice numeral 18 and la pressure chamber indicated in that ligure by the reference numeral 19. The pressure chamber 19 is at the one end of the cylinder 10 adjacent to the cap 12 and the outlet 13.

A coil spring 20 is disposed within the pressure charnber 1S and has one end bearing upon the adjacent face of the piston 16 and has the other end connected to the actuating member 14 by means of a spring coupling'21 and a snap ring 22 which lits within a groove formed in the outer side of the actuating member 14.

A reservoir 23 is provided on the top side of the cylinder 10 and has a passage 24 partially closed by a plug 25 connecting the reservoir with the pressure chamber 19.

Another passage 26 connects the reservoir with the equalizing chamber 18, there being a threaded plug 27 having a check valve therein threaded in the passage 26.

Filler caps 28 and 29 are provided in the upper end of the reservoir 23 and provide a means for installing the plugs 25 and 27 respectively.

A flexible conduit 30 connects the one end portion 15 of the actuating member 14 with the reservoir 23 so that fluid will ow from the reservoir 23 into the interior of the actuating member 14 and through a port 31 in one side of the actuating member 14 into the equalizing chamber 18 upon movement of the piston toward the outlet. A bleed hole is provided in the end of the cylinder adjacent the cap 11 and is closable by a threaded plug 32, and provides a means for bleeding off any air which might be entrapped within the equalizing chamber 18. j

The end of the actuating member 14 which is adjacent and projects into the pressure chamber 19 is provided with a threaded plug 33 having its end overlying the end of the actuating member 14 and providing a stop for the piston 16 so that upon retractive movement of the actuating member 14 from the pressure chamber 19 it will move the piston 16 along with it. Y

The threaded plug 33 is provided with a check valve 34 which prevents the flow of fluid from the pressure chamber 19 to the interior of the actuating member 14. A second coil spring 35 within the pressure chamber 19 serves to return the piston to its initial position upon retractive movement of the actuating member 14 from the pressure chamber 19. The end portion 15 of the actuating member 14 which projects from the cap 11 is provided with a ball joint connection to the brake pedal of the brake system, the connection being indicated in Figure 1 by the reference numeral 36. j

A packing ring 37 underlies the `cap 12 and seals that one end of the cylinder 10 fand packing rings 38 and 39 on the piston 16 and actuating member 14, respectively, serve to seal the pressure chamber 19 from the equalizing chamber 18, there being provided for the cap 11 a packing nut 4t? for enclosing and tightening the packing 41 around the actuating member 14. A resilient gland member 42, closes the end of the cylinder 10 adjacent to the cap 11 fand serves to further maintain the pressure of the iluid in the equalizing chamber 18.

In use, whenever the brake pedal (not shown) of the brake system applies pressure through its connection 36 to the end of the actuating member 14, the actuating member 14 will move inwardly of the cylinder 10 until the pressure of the iluid Within the brake cylinders on each wheel of the vehicle to which the system is applied and` the pressure in the pressure chamber 19 equals the pressure exertedby the spring 20 upon the one end of the piston facing the equalizing chamber 18. At this point, the piston will have moved in response to the pressure of the spring 20 and the movement of the actuating member 14 into the pressure chamber 19 closing the passage 24. Further movement of the actuating member 14 inwardly of the cylinder 10 will close the port 31 by moving "the actuating member relative to` the piston 16m. The iluid then within the equalizing chamber 18 will prevent backwardmovement ofthe piston 16 upon further increase ofY the pressure in the pressurev chamber 19 caused by the @werden atlas attuati-mammina.thereinto. whenY f `m` the actuating ,memberldisreleased, it will rr'ipvebaclgntoitsinitiallpogtion with respect to the piston 16, opening the port 31 so thatgthefluid within,V the equaliginghcharnber 12willowtbackward'through the interiorloflhe AactuatingI11rl1 .brf.iff-l tothe reservoir 23.l

The endfof'rtheplugfZS'projecting, into the, pressure chamber isnprovidedwith anfOring seal 43 fitting into ed. theplnend prejectingfmm the surwhaalbcr.. 12.,.by .the faction-.Cime wuafiaggmmber lileaadf slcpantidnwithfa :sprinaland-.therort 3 1. hasibe'en fclosedQ- by further, movement of vthe actuating memberA relative to, th e .pis ton 16, as shown in vdotted lines in liigurefl,l a'ny'1fur-ther application Vof pressure on.

the ralgeup'edal; will. cause Vthe actuating-member 14 to moveinto,the-pressure.chamber .19, increasing the pressure therein. Shouldthe pressure in the pressure` chamb e r ;19 ffbelostdue. to actuation. ofone of the brake cylinders in ,the l,systenrlor for other reasons, and pressure is.applied to -theactuating .member 14, the coil sp A20 will moVethepiston-l furtherinto the pressure chamberwll) andthe .passage 26 will permit further new of; fluid from .thereservoir into the equalizing chamber,1&,to make up forthis rmovement of the piston 16.

Further, shouldthe brakecylinders in the system be stilv due to frost or rust, or mechanical damage, so that` the spri1 1g20. yfailsto move thepiston 16 yas above descrzib beyond `the Lpoint where the piston has closed. the passagef24,..short. pumping strokes of the actuating, membei-will pumpuid through the check valve 34 in thefendofthe actuating member to increase the pressure, inthelpressure chamber.

It wiH be. seen, therefore, thatv-thearrangement of the.

space .Withinsaidcylinder into a fluid equalizing chamber anda uid pressure chamber, said pressure chamber being adjacent the. one endofsaid cylinder-having saidoutlet, resilientmeans. disposedwin said equalizing chamberand operatively connected. .to said piston-and-tokthe adjacentv part of. said actuating member for biasing said piston toward.tsaidcpressure.- chamber, a reservoir, a ilexible conduiticonnecting said-onecnd portion-of-said actuating member'with=said reservoir,- a port `in the' sidejiof said actuating-member.'adjacent theV end of said piston facingsaid equalizingchamber, the other -end of said-otherend portion-pffsaid actuatingmemberhaving a check valveI for-preventing the flow ofluidfrcm the-pressure cham-A urechamberwiththe piston and the actuating mem;

draulic .rnastergcylinder comprising a cylinder:-

ber to the interior of said actuating member, said piston being operable to close said port upon initiation ofin'ov'e-` ment of said actuating member toward said outlet and into said pressure chamber after the pressure of fluid in said pressure chamber equals the pressure exerted by said resilient means on said piston whereby fluid in said equalizing chamber is locked-.and-prevents movement of said piston outwardly from said pressure chamber, and a spring-in said pressurechamber for'movingfsaidepiston outwardly? therefrom uponfretraction 0fsaid actuating member from said pressure chamber.

2. A hydraulic master cylinder assembly comprising a cylinder having bothlendsclosed and providednlwith an outlet in one of,v said ends;l al hollowf actuating member having closed ends mounted within said cylinder for re ciprocal movement toward and away from said outlet and having one end portion exteriorly of the other end of said, cylinder,l ,ant annular piston. Vslidably. carried byv the other., end .portio'n .of said Iactuating, mernber subdividi'ng the SpaceWthin said cylinder intoa fluid equalizingchamvn ber. :and aA fluidv pressure chamber, said; pressure f chamber being, adjacent -theqoneendof .said cylinder .having said; outlet,v resilient.. means-, disposed i within said .equalizingt chamber and'operatively connectedrtosaid pistonandto. the` adjacent part lof .said actuating member for biasing said piston toward said .pressure .chambena reservoir hav ing. a Ypassage ...connecting said, reservoir with said presv.- sure, chamber, a flexible conduit connecting said one end portionof-said actuating member with said reservoir, ay port in the side of said actuating member adjacent to the,- end..of said'trpiston facing :the equalizing chamber, the othergendvof saidfotherfend portion of said actuating member..having vaucheck` valve 'for .preventing lthe.- iloiv` affluid fromthe pressure chamber to the interior .of said..y actuating member, said piston being operable to close said. passage uponinitiationy of.; movement of said actuation memben-towardsaid outlet .and to. close said port upon initiation offurt'ner movement fof said actuating member toward said outlet and into said pressure charnberiafter the `:pressureof uidfinsaid pressure chamber. equals ther'pressureexertedfby 'said y resilient Vmeans on .said pis;A tort-t wherebyijuid ,in=:said :equalizing -chamber. is. Llocked and prevents movement -of said piston outwardly trom said .:pressure f-cliamber,V said reservoirI being provided with a check-valved'passage 2connecting.saidreservoir with` .saida equalizingv chamber and. preventing iluid'jfl-w from said equalizing ch'amber into said reservoir, anda springsin;I said;l pnessurerfchamber: for moving said piston outwardly therefrom upon retraction of said actuating: membertfrem said pressure chamber.

3. A hydraulic master cylinder assembly comprising; a cylinder havinguboth.- endsy closed .and provided with an.,;outlet' fin.:onelofrsaidvends; ya hollowactuating memiv ber havingqclosedfcnds mountedy within said. cylinde'rfol'iv reciprocal movement-,toward and away.'from'saidloutlet. .andyhayingonezenduportion exteriorly'fof the other end ofxsaidscylinder, anuannularapiston. slidably carriedby the #other xend .portion of; the actuating member'.su'bdivi'd*- ing the space within said cylinder 4into a fluid equalizing chamberffandva Afluid. pressure'chamber, said pressure chambe'ra'being :adjacent theion'e endof said cylinder .havingsaidoutlet, resilient means disposed within said equalizingtchamber'and. operatively connected tosaid piston `and tto:thejfadjacenttpart:ofusaid actuating memberfor biasing said pistontowardy said pressure'chaniber, a reservoir having a passage `connecting said reservoiry with' saidLpress-ure=chamber; a flexible conduit connecting said -one-.end'portionof saidactuating` membery with said reservoir,...a porttinstheside of said actuatinglmember ald jacentftheend:ofsaid. piston'facing said equalizingcham# ber, said piston being operable to cl-osesaid passagevupon initiation ofzmovement` of-said actuating member toward said outlet'-and-torclosefsaid port upon initiation offurther;- movement of-f-said Vactuating 1memberctovvard -"said out-let'fand intoA saidv pressure chamber 'after the` pres# sure of uid in said pressure chamber equals the pressure exerted by said resilient means on said piston whereby duid in said equalizing chamber is lock-ed and prevents movement of said piston outwardly from said pressure chamber, said reservoir being provided with a check valved passage connecting said reservoir with said equalizing chamber .and preventing fluid flow from said equalrizing chamber into said reservoir, said actuating member lbeing provided wit-h a check-valved passage in the end of said actuating member adjacent said pressure cham- 4ber preventing fluid ow from said pressure chamber into said actuating member, and Ia spring in said pressure cham- References Cited in the file of this patent UNITED STATES PATENTS 1,604,545 Bragg et al. Oct. 26, 1926 2,317,4734 Miller A Apr. 27, 1943 2,358,021 Miller Sept. 12, 1944 2,415,245 Hopmans Feb. 4, 1947 

